Definitions
1.noun(earth sciences) The line at which the earth and sky meet.
2.nounThe horizontal silhouette of a city or building against the sky.
3.nounA path of movement, especially military movement, producing a silhouette above terrain features visible from the location of likely observers.
4.nounA panel on the front page of a newspaper outlining some of the features to be found inside.
5.verbTo outline something against the sky.